Catheters are commonly used in surgical procedures to access certain areas of a patient=s body without resorting to invasive surgical procedures. For example, catheters are widely used in the field of cardiology to conduct electrophysiological studies in which electrical potentials within the heart are mapped to determine the cause and location of arrhythmia. In many cases, certain undesired conductive pathways, known as foci, contribute to and cause the arrhythmia. Once the location of foci is identified, elements on or within the catheter can be utilized to ablate or isolate the foci, thus eliminating the arrhythmia.
One form of arrhythmia is atrial fibrillation, which is an uncoordinated contraction of the heart muscle within the atrium. Atrial fibrillation results from rapidly discharging foci and causes irregular heart beats, possibly leading to inefficient pumping of blood. In a significant number of patients, the foci that contribute to this condition are located within the pulmonary vein, adjacent to the atrium. These foci may be in the form of scattered groups of rapidly discharging cells. Treatment of this condition can sometimes be effective through the ablation of these foci. However, identifying the location of these foci and effecting the ablative treatment of the foci can be time consuming and difficult.
A variety of cardiac mapping and ablation catheter systems are well known in the art. For example, U.S. Pat. No. 5,476,495 (Kordis et al.) discloses a steerable catheter system that is able to conduct cardiac mapping and ablation. U.S. Pat. No. 5,507,743 (Edwards et al.) discloses a radio frequency (RF) treatment apparatus that includes a RF electrode that assumes a helical orientation upon deployment. U.S. Pat. No. 5,738,683 (Osypka) discloses a cardiac mapping/ablation catheter that includes an electrode that may be deployed in the shape of a loop. U.S. Pat. No. 5,782,879 (Imran) discloses an endocardial mapping and ablation system in which the catheter includes a deployable distal extremity, in the form of a cage-like member that includes a plurality of electrodes.
Despite the existence of these references and existing ablation catheter systems, there exists a need to provide a system that is able to effectively treat atrial fibrillation conditions that are caused by foci present within the pulmonary vein.